The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies.
Computer and network systems are subject to a variety of attacks such as viruses, worms, trojans, unauthorized users, an individual bot or a botnet. A botnet is a collection of internet-connected programs communicating with other similar programs in order to perform tasks. These can be as mundane as keeping control of an Internet Relay Chat (IRC) channel, or malicious, as in the case of sending spam email, participating in distributed denial of service (DDoS) attacks, or other malicious activity. Typically a botnet refers to any group of computers, often referred to as zombie computers or bots, that have been recruited by executing malicious software. A botnet's originator, typically known as a “botherder” or “botmaster,” can control the group remotely, usually through an IRC channel, and often for criminal purposes. The botnet originator can communicate through the IRC channel via a server, known as the command-and-control (C&C) server. The means for communication in a centralized architecture is either IRC protocol or Hypertext Transfer Protocol (HTTP). The IRC protocol allows the botmaster to have real time communication with the bots. In the HTTP protocol, the botmaster does not communicate directly with the bots but rather, the bots periodically contact the C&C server to obtain their instructions. Some newer botnets communicate using a decentralized architecture by employing peer-to-peer (P2P) communication, with command-and-control embedded into the botnet rather than relying on C&C servers, thus avoiding any single point of failure.
A firewall is a set of related programs used to help keep a network secure. Its primary objective is to monitor and control the incoming and outgoing network traffic by analyzing the data packets and determining whether each packet should be allowed through or not, based on a predetermined rule set. Features of a firewall may include logging, reporting, and a graphical user interface for controlling the firewall.